In the course of resurfacing a concrete or asphalt pavement, the upper surface of the worn pavement is removed by a machine having a rotating drum and a plurality of rotatable tools mounted on the drum. Each tool is mounted by first welding to the drum a base block mounting having a bore suitable for receiving the shank of a removable quick-change tool holder. Fitted into the bore of the base block mounting is the shank of a replaceable quick-change tool holder having a retaining bore at the forward end for retaining the shank of a tool.
Where the tools are used to cut hard surfaces such as asphalt or concrete, the tools retained in the quick-change tool holder must rotate to wear evenly around their circumference and thereby maximize their useful life. A hard surface engaged by such tools nonetheless wears the tool rapidly. When the machine is used to cut hard surfaces it is common to replace the tools at least once a day. The hard surface that causes the tool to become rapidly worn also wears the tool holder that receives the rotatable shank of the tools. Although life expectancy of the tool holders may be several times longer than the life of the tools received therein, extended use of the machine will result in the tool holders becoming worn and requiring replacement.
A quick-change tool holder generally has a tapered forward end and extending axially rearwardly of the tapered forward end is a shank that is received in the complementarily shaped bore of the base block mounting on the machine. Preferably, the quick-change tool holder is the type disclosed in my previously issued U.S. Pat. Nos. 6,371,567 B1 and 6,585,326 B2, which are incorporated herein by reference.
Ideally, worn quick-change tool holders are removed from the base blocks of the machine using a punch and hammer to withdraw the shank from the bore of the base block mounting. The strong forces that are applied to the tools are also applied to the tool holders and the base block mountings as the machine cuts the hard surfaces, and those forces cause the various parts to become deformed such that the shank and quick-change tool holders cannot be easily extracted from the bore of the base block mounting. The problem becomes more complicated for tool holders mounted near the peripheral edges of the drum because several of such end mounted tool holders are oriented at an angle with respect to the drum that allows little or no access to the rearward end of the shank thereof. It is therefore difficult or nearly impossible to remove such quick-change tool holders from the retaining bore, and it is often necessary to use a torch to cut away portions of the worn tool holder in order to replace it.
In my co-pending patent application filed Dec. 4, 2006 and assigned Ser. No. 11/633,298 I disclosed a retraction device for retracting a quick-change tool holder from the bore of a base block mounting that includes an elongate shaft that extends through the bore of the quick-change tool holder with a nut, or other enlarged object positioned at the distal end of the shaft such that the nut and shank can be used to extract the tool holder from a base block mounting. Where the quick-change tool holder includes a moveable plunger, however, the use of the device of Ser. No. 11/633,298 requires that the plunger be first removed. There is therefore a need for a retraction device for retracting a quick-change tool holder from the bore of a base block mounting without requiring access to the rear end of the shank of the quick-change tool holder. There is also a need for a retraction device that does not require the removal of the plunger from the quick-change tool holder before the tool holder can be removed from the base block mounting.